The use of lasers, as controllable sources of relatively monochromatic and coherent radiation, is becoming increasingly common in diverse fields such as telecommunications, data storage and retrieval, entertainment, research, and many others. In the area of medicine, for example, lasers have proven useful in surgical and cosmetic procedures in which a precise beam of high energy radiation can cause localized effects through photothermal processes (e.g., selective photothermolysis) and/or photomechanical processes (e.g., induction of cavitation bubbles and acoustic shock waves). In dermatology specifically, lasers have been used in a wide variety of procedures including hair removal, skin resurfacing, removal of unwanted veins, and the clearance of both naturally-occurring and artificial skin pigmentations (e.g., birthmarks, port wine stains, and tattoos).
Whereas early laser tattoo removal procedures often utilized non-selective ablation of tissue at the tattoo site with water serving as the target chromophore, recent procedures have instead utilized Q-switched lasers capable of producing high-powered, nanosecond pulses to induce photomechanical breakdown of the tattoo particles themselves. In addition to pulse duration and power, the wavelength of the radiation is also an important parameter in the efficacy of a treatment. For example, though alexandrite lasers emitting picosecond pulses at wavelengths between 750 and 760 nm have been found to be especially effective at treating black, blue, and green tattoo pigments (Brauer et al., “Successful and Rapid Treatment of Blue and Green Tattoo Pigment With a Novel Picosecond Laser,” Archives of Dermatology, 148(7):820-823 (2012)), radiation in the 750-760 nm range is not nearly as effective in removing red or orange tattoos due to the low absorption coefficient of orange and red tattoo pigments at such wavelengths.
Accordingly, there exists a need for improved methods and apparatus for producing ultra-short pulses of laser radiation at various wavelengths for the treatment of tattoos, pigmented lesions, and other skin disorders.